Consumers continually seek to improve the appearance of their skin and hair. Concerns include visible signs of aging, as well as discoloration or hyper-pigmentation, redness and/or inflammation; and over-production of oils and lipids at the skin surface. Thus there remains a need for products that provide anti-aging, anti-inflammatory, anti-lipid and/or lightening effects.
Skin and hair pigmentation is determined by the level of melanin present in the epidermis or hair fiber. Three different types of melanin are present in the epidermis: DHI-melanin, which is blackish in color; DHICA-melanin, which is brownish; and pheomelanin, which is reddish in color. Melanin is synthesized in specialized organelles called melanosomes within pigment cells (melanocytes), in a process that begins with the action of an enzyme, tyrosinase, on the amino acid tyrosine. Melanin synthesis is regulated by a number of intracellular factors such as the activity of tyrosinase, the activity of micropthalmia-induced transcription factor (MITF), signaling by hormones such as melanocyte-stimulating hormone (MSH), oxidative stress, and other factors.
Inflammation also contributes to skin discoloration and has other deleterious effects on the appearance of skin. Ruiz-Maldonado et al. (1997) Semin Cutan Med. Surrg. 16(1):36-43; Tomita et al. (1989) Dermatologica 179 Suppl 1:49-53. For example, inflamed acne lesions can lead to scarring (Holland et al. Semin Cutan Med Surg. 2005 June; 24(2):79-83); and the cumulative degenerative effects of inflammation have been shown to exacerbate intrinsic (chronological) and extrinsic (photo) aging of human skin. Pillai, et al. (2005) Int J Cosmet Sci. February; 27(1):17-34; Bissett, et al. (1990) Photodermatol. Photoimmunol. Photomed. 7:153-8; Thornfeldt, C R (2008) J. Cosmet. Dermatol. 7:78-82. A key inflammatory mediator, tumor necrosis factor-alpha (TNFa), is believed to be responsible for both acute and chronic skin inflammation.
Collagen synthesis and degradation also play a role in common skin concerns. Reduction in collagen I, the collagen type in skin, is associated with loss of firmness and elasticity of skin and leads to wrinkling associated with aging. Collagen is the body's major structural protein and gives skin strength, durability, and a smooth, plump appearance. It is created by fibroblasts, specialized skin cells located in the dermis, in a process that involves conversion of preprocollagen I to procollagen I and eventually to tropocollagen, the form that forms collagen fibers. Collagen I is degraded in the skin by matrix metalloproteinases (MMPs). Gross J, et al. Biochem Biophys Res Commun 1974; 61:605-12. MMPs are a family of related zinc-dependent proteases, including the metalloproteinases (MMP-1, -8, and -13) and gelatinases (MMP-2 and 9).
Hyaluronic acid is another component of skin that plays a role in its aesthetic appearance. Hyaluronic acid is a glycosaminoglycan (GAG) found in the skin, as part of the extracellular matrix (ECM). With age, however, GAG synthesis and overall GAG skin content appear to decline. Smith et al. J. Invest. Dermatol., 1962, 39, pages 347-350; Fleischmajer et al. Biochim. Biophys. Acta, 1972, 279, pages 265-275; Longas et al. Carbohydr. Res., 1987, 159, pages 127-136. It is believed that this reduction in GAG contributes to age-related changes in the skin's mechanical properties, including, for example, changes in tissue hydration, as well as plumpness and protection against free radicals. Carrino et al., Arch Biochem Biophys. 2000 Jan. 1; 373(1):91-101; Vogel et al., Z Gerontol. 1994 May-June; 27(3):182-5; Lanir et al., J Biomech Eng. 1990 February; 112(1):63-9); Wiest et al. J Dtsch Dermatol Ges. 2008 March; 6(3):176-80; Bert et al. Biorheology. 1998 May-June; 35(3):211-9.
The activity of exfoliating enzymes in the skin also plays a role in its aesthetic youthful appearance. In the stratum corneum, skin's outermost layer, cell-to-cell cohesion depends primarily on proteins known as the corneodesmosomes. During skin remodeling and renewal, dead cells are shed from the skin surface by the action of native proteases that break down the corneodesmosomes, thus helping exfoliation. Human tissue Kallikreins (KLKs) are a family of proteases that reside in the stratum corneum and are known to be directly involved in corneodesmosome turnover. Kishibe M et al. J. Biol. Chem. 2006; 282: 5834-5841.
Overproduction of lipids also affects the appearance of skin, as well as that of hair. For example, excess secretion of sebum is associated with oily skin, hair, and acne; and excess accumulation of subcutaneous fat can result in cellulite. Cellulite is a lumpy, uneven type of fat, that accumulates primarily on the buttocks and thighs and causes an “orange peel” or “cottage cheese” look. Lipid metabolism is partly controlled by the peroxisome proliferator-activated receptors (PPARs), which form a group of nuclear transcription factors. PPAR-gamma (PPAR-γ), in particular, is believed to be critical in a feed-forward pathway that favors differentiation of and energy storage by adipocytes.
Many of the physiological processes in play in the development of undesirable skin or hair have counterparts in eukaryotic microorganisms, such as yeast, and yeasts extracts have been used in cosmetic applications. For example, in response to heat, UV radiation, or other stress, yeast are known to produce factors that promote cell proliferation or viability. See, e.g., U.S. Pat. No. 2,239,345. Stressed yeast lysates containing such factors have been described and have been indicated for use in cosmetic applications directed to counteracting the effects of certain stresses on the skin. For example, UV-stressed yeast lysates have been used in cosmetic applications. See, e.g., U.S. Pat. Nos. 5,643,587; 5,676,956; and 5,776,441. More recently, ozone-stressed yeast lysates have been described as useful in protecting skin cells from the harmful effects of ozone. See, e.g., U.S. Pat. Nos. 6,461,857 and 6,858,212 to Scholz et al; and U.S. Pat. Appl. Pub. Nos. 2003/0198682 and 2006/0110815. Nonetheless, these earlier cases failed to recognize certain cosmetic uses and failed to identify active ingredients within the cellular lysates.
Accordingly, there remains a need for better-defined cosmetic compositions that effectively provide additional skin benefits, including exfoliating, anti-aging, anti-lipid, anti-inflammatory, and/or skin (or hair) lightening effects. It is therefore an object of the invention to provide compositions and methods for decreasing melanin synthesis, TNFa production, PPARs signaling, and/or metalloproteinase activity; and/or for increasing collagen synthesis, hyaluronic acid production, and/or KLKs activity. It is a further object of the invention to improve overall appearance of skin and hair, and to lighten the skin and hair as desired, by use of such compositions.
The foregoing discussion is presented solely to provide a better understanding of the nature of the problems confronting the art and should not be construed in any way as an admission as to prior art nor should the citation of any reference herein be construed as an admission that such reference constitutes “prior art” to the instant application.